Semiconductor chips used in electronic devices comprise a semiconductor die mounted on a carrier or a substrate. In an effort to increase the density and functionality of a semiconductor chip, attempts have been made to create 3D-ICs, or three-dimensional integrated circuits. Generally, 3D-ICs comprise a plurality of semiconductor dies stacked upon each other, such as one semiconductor die bonded on top of another semiconductor die. Electrical connections electrically couple contact pads on each of the stacked semiconductor dies to external contacts. The dies may include different functionality or simply increase the density of a single functionality, such as a memory.
Generally, attempts at creating 3D-ICs have included bonding a first wafer on which a plurality of dies has been formed to a second wafer, also on which a plurality of dies has been formed. The wafers are aligned such that the dies of one wafer are aligned with dies of the other wafer. As mentioned above, the dies of the wafers may have a different function or provide increased density for a single type of function, such as memory. Once bonded, a thinning process is typically performed to form electrical connections, typically by exposing a through silicon via that is electrically coupled to the bottom wafer. During the thinning process, however, the wafer often cracks and chips because the edges of the wafer are unsupported.
One attempt at preventing cracks and chips during the thinning process involved etching a notch along the periphery of the wafer to be thinned. Another attempt involved sawing an edge of the wafer to be thinned off, and then thinning the wafer. These attempts, however, reduce the wafer size and often include additional timely processes. Furthermore, these attempts may also require specialized equipment or may be incompatible with processes used by some fabricators.
Accordingly, there is a need for an efficient and effective method to create a stacked wafer configuration.